-- Performance Medicine Institute is pleased to announce the publication of a peer-reviewed study examining skeletal muscle mass and strength during substantial weight loss in men receiving a comprehensive tirzepatide-based treatment program. Published August 10 in Obesity Pillars, the study followed 93 men with obesity and symptoms of testosterone deficiency for up to 12 months.
The paper, “Increasing Skeletal Muscle Mass and Strength During Incretin-Based Weight Loss,” enters a public discussion that has largely centered on a single concern: whether weight lost with GLP-1 medications also includes a meaningful amount of muscle. Researchers and authors of the paper, Christopher L. Mendias, PhD, ATC, and Tariq M. Awan, DO, examined a broader question—whether substantial fat loss can occur alongside improvements in estimated skeletal muscle mass, strength and physical function when several aspects of health are addressed together.
The retrospective case series included 48 participants without type 2 diabetes and 45 with the condition. All received tirzepatide, marketed as Mounjaro and Zepbound, as well as testosterone therapy for symptomatic testosterone deficiency with qualifying laboratory findings. The program also incorporated resistance exercise, high-protein nutritional counseling and weekly lifestyle and behavioral coaching. Participants were counseled to pursue more than 150 minutes of exercise weekly, with approximately 60% to 70% devoted to resistance training, and to target 150 to 200 grams of protein per day.
At 12 months, body weight had declined by approximately 18% to 20%, while fat mass fell by approximately 38% to 40%. Estimated skeletal muscle mass increased by approximately 4% to 12%, and grip strength rose by approximately 18% to 21%. Among participants with type 2 diabetes, average HbA1c decreased from 10.1% to 5.8%. The study also reported reductions in LDL cholesterol and high-sensitivity C-reactive protein, together with improvements in patient-reported physical and mental health scores.
“There has been a lot of attention paid to how much weight people can lose with GLP-1 medications, but we think an equally important question is what kind of weight they are losing,” says Dr. Awan, Medical Director of Performance Medicine Institute. “The goal should not simply be a lower number on the scale. Ideally, we want patients to lose excess body fat while preserving or improving skeletal muscle, strength, metabolic health and physical function. Our findings suggest that substantial weight loss and improvement in muscle health can occur at the same time.”
A key point in the paper is the distinction between lean body mass and skeletal muscle mass. Lean body mass is a broad measure that includes muscle, organs, body water, glycogen-associated water, connective tissue and other nonfat tissue. In the study, total lean body mass decreased, yet estimated skeletal muscle mass and grip strength increased. The authors noted that a decline in measured lean mass should therefore not automatically be interpreted as an equivalent decline in skeletal muscle.
For patients arriving at a weight-management appointment, the scale is often the most visible marker of progress. The research suggests that the story beneath that number may be equally important. Body composition, strength, metabolic measures and day-to-day physical function can offer a more complete view of how treatment is affecting health.
The findings do not establish that skeletal muscle gain will occur with tirzepatide alone. The participants received multiple interventions at the same time, and the analysis was limited to men with obesity and testosterone deficiency treated at a single outpatient clinic. As a retrospective case series without a comparison group, the study supports further investigation rather than a conclusion that any one component caused the reported changes. Testosterone therapy is appropriate only for patients who have been clinically evaluated and meet treatment criteria.
The article is available at https://doi.org/10.1016/j.obpill.2026.100317. Please also visit https://www.performancemedinst.com for more information.
About Performance Medicine Institute
Performance Medicine Institute is a multidisciplinary medical practice in Phoenix, Arizona, that combines medicine, rehabilitation, exercise science, metabolic health and performance-focused care. Its clinical services span men’s health, hormonal and metabolic health, obesity and diabetes, musculoskeletal and sports medicine, rehabilitation, pelvic and sexual health, athletic performance, recovery and healthy aging. The practice uses an integrated clinical model influenced by professional and collegiate sports medicine, where medical treatment, rehabilitation, exercise, nutrition, recovery and physical performance are managed as connected aspects of care.
Performance Medicine Institute is co-directed by Christopher Mendias, PhD, ATC, Director of Rehabilitation and Research. A rehabilitation clinician-scientist, his work examines muscle, tendon, bone and cartilage healing and regeneration, along with metabolism and endocrine disorders. Dr. Mendias earned bachelor’s degrees in athletic training and biology and a master’s degree in physiology from the University of Arizona. He received his PhD in molecular and integrative physiology from the University of Michigan Medical School and subsequently completed a postdoctoral fellowship in biomedical engineering. His earlier appointments include serving on the faculty of the University of Michigan, the scientific staff of Hospital for Special Surgery in New York and the faculty of Weill Cornell University. He has authored more than 100 scientific research papers and book chapters, with research support from the National Institutes of Health, the Department of Defense and several foundations.
Co-director and Medical Director Tariq Awan, DO, is double board certified in sports medicine and family medicine. He earned his medical degree from the Chicago College of Osteopathic Medicine at Midwestern University, completed his residency at Henry Ford Health System in Detroit and served as chief resident before undertaking a sports medicine fellowship at Mayo Clinic. His professional and collegiate sports medicine experience includes serving as head team physician for the Orlando Magic and working with the medical staffs of the Detroit Pistons, Detroit Red Wings, Detroit Tigers and University of Michigan Wolverines. Dr. Awan’s clinical interests include sports and musculoskeletal medicine, chronic muscle and tendon disorders, osteoarthritis, concussions, osteoporosis and biologic treatments for musculoskeletal conditions. He is also an active researcher who has directed clinical trials and contributed to numerous scientific publications.
Scientific research is a central part of the institute’s work. Its team has contributed to more than 100 scientific publications in addition to clinical trials and laboratory studies. Performance Medicine Institute is located at 3330 N. 2nd Street, Suite 401, Phoenix, Arizona 85012.
Contact Info:
Name: Santos Verdugo
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Organization: Performance Medicine Institute
Phone: 602-606-8949
Website: https://www.performancemedinst.com
Release ID: 89200910
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